A greater understanding of the mechanisms mediating melanoma metastasis is necessary for treatment of advanced disease. Because all melanoma cells must move through and survive in non-native tissue microenvironments during metastatic dissemination, the ability to migrate and survive in these microenvironments is critical for metastatic potential. We and others have observed that melanoma cells encapsulated in 3-dimensional extracellular matrices that mimic soft tissues exhibit spontaneous and continuous non-apoptotic membrane blebbing. These observations have led us to ask if membrane blebbing is associated with the ability to survive and migrate through soft tissues. We propose to study the mechanisms that may enable melanoma migration and survival during metastatic dissemination as a function of membrane blebbing. Thus, the scientific objective of this project is to determine how blebbing is related to metastatic dissemination in melanoma. At the completion of this project, we will have determined if blebbing is enriched in stage III melanoma samples that exhibit efficient metastasis compared to stage III samples that exhibit less efficient metastasis, and we will have determined if these differences in metastatic efficiency are mediated by the scaffolding function of the ERM family protein ezrin. We will have determined if the spatiotemporal organization of phospholipid signaling regulates ezrin phosphorylation to organize membrane blebs that facilitate cell migration in 3D matrices, and we will have determined if membrane blebbing facilitates survival signaling by regulating the spatial partitioning of ezrin between membrane and cytosolic compartments. The training objective of this proposal is to train Dr. Erik Welf in the skills required to become an independent investigato specializing in quantitative approaches to dissect the mechanisms underlying metastatic dissemination of melanoma. The proposed training activities will complement Dr. Welf's previous experience in computational modeling and analysis by providing training in the cutting edge molecular biological, imaging, and in vivo approaches necessary to study the processes of metastatic dissemination in realistic microenvironments. The proposed project leverages the expertise of faculty mentors Gaudenz Danuser and Sean Morrison, who are experts in the fields of live cell imaging and in vivo approaches, respectively. The dynamic interplay between analytical and experimental approaches is fundamental to the approach that Dr. Welf will apply as an independent researcher, and this training experience will complete the skills to facilitate this approach. Although few, if any, existing laboratories can boast expertise in both analytical and experimental approaches relevant to melanoma, the proposed mentorship team will enable Dr. Welf to develop the skills required to become successful in this endeavor.